1. Field of the Invention
The present invention is broadly concerned with an expansion joint structure particularly useful in the context of floor expansion joints and which exhibits three degrees of freedom in order to accommodate virtually all relative movement between adjacent structural sections. More particularly, it is concerned with such an expansion joint which is preferably constructed to be fire-rated and which maintains its fire rating even upon relatively significant movement between adjacent structural sections which has been known to destroy the integrity of prior fire-rated designs.
2. Description of the Prior Art
Expansion joints have long been used in floors and walls of buildings in order to accommodate normal relative shifting movement occurring by virtue of settling or thermal cycling. In the case of floor expansion joints, such have included a pair of extruded aluminum supports fixed to adjacent joint-defining floor sections together with a cover in overlying relationship to the joint and operably affixed to the supports to maintain its covering relationship even during normal movement of the floor sections.
In recent years, architects have increasingly demanded that expansion joints be fire-rated, at least to the rating of the adjacent walls or floor sections. Thus, U.S. Pat. No. 4,706,426 describes an innovative fire-rated flush mounted corner guard designed to give fully adequate fire rating at least up to the level of the adjacent walls.
It has also been known in the past to provide fire-rated floor expansion joints. Such units have typically included a generally U-shaped in cross-section bridging member between adjacent floor sections and constructed of fire-resistant material. A problem with such prior joints, however, is that they are unable to accommodate three degrees of relative movement of the floor sections while still retaining their fire rating. Thus, in such designs, where the floor sections shift longitudinally relative to each other, the U-shaped bridging member tends to tear or detach, thus impairing its fire rating.
Another type of floor expansion joint heretofore proposed comprises a pair of U-shaped metallic supports affixed to each floor section at the joint area and facing each other; a concrete pad or treadway is received by the facing U-shaped supports. This type of construction can accommodate longitudinal shifting of the floor sections, and also movement of such sections towards and away from each other. However, it cannot properly accommodate relative vertical shifting of the floor sections.
Accordingly, there is a decided need in the art for an improved expansion joint structure which exhibits three degrees of freedom and which, if desired, can be constructed of fire-rated materials. In this fashion, the joint structure can maintain its original fire rating notwithstanding relatively significant movement of the joint-defining structural sections.